Base station, subordinated station and transmission method thereof

ABSTRACT

A base station (BS), a subordinated station (SS) and the transmission methods thereof for use in a multi-input multi-output (MIMO) network are provided. The BS stores resource allocation information about the MIMO network and an SS list, and generate a super frame according to the resource allocation information and the SS list. The super frame comprises a pilot pattern which comprises a plurality of pilots and data. The BS and SS both considers the pilot pattern as an identifier of the SS. When there are communications occurred between the BS and the SS, the BS/SS will confirm whether the pilot pattern of the super frame matches the identifier of the SS to reduce interference from other stations in the MIMO network.

This application is a continuation-in-part application of applicationSer. No. 12/435,792 filed on May 5, 2009, which application claims thebenefit of priority based on U.S. Ser. No. 61/050,351 filed May 5, 2008,the disclosures of which are incorporated herein by reference in theirentirety. This application also claims the benefit of priority based onU.S. Ser. No. 61/078,666 filed on Jul. 7, 2008, the disclosure of whichare incorporated herein by reference in their entirety.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a base station, a subordinated stationand transmission methods thereof. More specifically, the presentinvention relates to a base station, a subordinated station andtransmission methods thereof complying with an IEEE 802.16 m standard.

2. Descriptions of the Related Art

With continuous advancement in science and technology, people areimposing ever higher requirements on communications. Nowadays, more andmore importance is being attached to convenience of communications inaddition to requirements on quality of communications. Wirelesscommunications are advantageous in that they provide higher mobility byobviating the need of physical communication network wiring. Therefore,wireless-communication-enabled products such as mobile phones, notebookcomputers and the like are more and more popular in recent years andhave become the mainstream products in the consumer electronics market.

In the conventional wireless networks, there are four kinds ofinterference types in transmission: data transition in time divisionduplex (TDD), data transition in frequency division duplex (FDD), theinterference in central zone edge, and the interference in cell zoneedge.

Particularly, please refer to FIG. 1A, which is a schematic view of atransmission cell 1 a in the conventional wireless network. Thetransmission cell 1 a comprises a plurality of central zones 100, 104,108, a plurality of cell edge zones 102, 106, 110, a base station (BS)111 a, a plurality of subordinated station (SS) 103, 105, 107, 109, 111,113, 115, 117 corresponding to the BS 101 a. First, the interference ofthe data transition in TDD is described. In the different central zones,if down link (DL) and up link (UL) between the BS 101 a and the SSs areoperated at the same time, the different SSs may have interference inthe data transmission.

The interference of the data transition in FDD occurs in this situationthat if the different SSs operate at the same frequency, the SS mayreceive another SS's signal and get interference. The interference incentral zone edge means that if the SS is positioned in the edge of thecentral zone, it may receive the two kinds of signals from the twodifferent central zones, and one of the signals received by the SS isthe interference. For example, the SS 117 may receive the two kinds ofsignals from the central zones 100 and 104, and one of the signalsreceived by the SS 117 is the interference. Similarly, the SSs 109 and113 may meet the same interference as the SS 117, and will not bedescribed again.

The interference in cell zone edge means that if the SS is positioned incell zone edge and the BS's signal power is lower, it may receiveanother BS's signal to make interference. For example, the SS 107 ispositioned in the edge of the cell zone and the BS's 101 a signal poweris lower, the SS 107 may receive another BS's signal to makeinterference. Similarly, the SSs 111 and 115 may meet the sameinterference as the SS 107, and will not be described again.

Moreover, please refer to FIG. 1B, which is a schematic viewillustrating the transmission cell 1 a and a transmission cell 1 b inthe conventional wireless network. As shown in FIG. 1B, the SS 111 iswithin the signal coverage between the transmission cell 1 a and thetransmission cell 1 b. Specifically, the SS 111 is in a cell zone edgeof the transmission cell 1 a and the transmission cell 1 b, and iscommunicating with the BS 101 a of the transmission cell 1 a and a BS101 b of the transmission cell 1 b at the same time, which often occursin a handover procedure. However, the SS 111 may receive signals fromthe BS 101 a and the BS 101 b meantime, and the interference occurs incell zone edge accordingly to effect the communication quality.

In summary, the aforementioned interference affects the quality ofcommunications between the BS and the SS in the wireless networkseriously. How to reduce the interference in the wireless networkefficiently is still an objective for the industry to endeavor.

SUMMARY OF THE INVENTION

The primary objective of the present invention is to provide a basestation (BS) for use in a multi-input multi-output (MIMO) network. TheMIMO network includes another BS and a subordinated station (SS). The SSis within a signal coverage between the BS and the another BS. Theanother BS communicates with the SS by at least one first pilotstructure in a first super frame. The BS comprises a transceiver, astorage module and a generation module. The transceiver is configured toreceive the first super frame. The storage module is configured to storepilot structure information. The generation module is configured toselect at least one second pilot structure of a second super frameaccording to the pilot structure information and the at least one firstpilot structure of the first super frame to generate the second superframe with the at least one second pilot structure. The at least onesecond pilot structure is orthogonal to the at least one first pilotstructure. The transceiver of the BS may communicates with the SS by thesecond super frame with the at least one second pilot structure to avoida transmission interference between the BS and the another BS.

Another objective of the present invention is to provide a transmissionmethod for use in a BS of an MIMO network. The BS comprises atransceiver, a storage module and a generation module. The storagemodule stores pilot structure information. The MIMO network systemincludes another BS and an SS. The SS is within a signal coveragebetween the BS and the another BS. The another BS communicates with theSS by at least one first pilot structure in a first super frame. Thetransmission method comprises the following steps: enabling thetransceiver to receive the first super frame; enabling the generationmodule to select at least one second pilot structure of a second superframe with according to the pilot structure information and the at leastone first pilot structure of the first super frame to generate thesecond super frame with the at least one second pilot structure; andenabling the transceiver to communicate with the SS by the second superframe with the at least one second pilot structure to avoid atransmission interference between the BS and the another BS.

The present invention uses different pilot structures, which areorthogonal to each other, in the BSs to transmit the data to the SS.These two different BSs may communicate with an SS in differentfrequency/channel by using the different pilot structures orthogonal toeach other. The transmission interference, which occurs when the SS iscommunicating with the different BSs at the same time, may be reducedeffectively. Thereby, the defects of the conventional technique may beovercome effectively, and the quality of communications may be enhancedobviously.

The detailed technology and preferred embodiments implemented for thesubject invention are described in the following paragraphs accompanyingthe appended drawings for people skilled in this field to wellappreciate the features of the claimed invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a illustrates a transmission cell 1 a in the conventionalwireless network;

FIG. 1 b illustrates the transmission cell 1 a and a transmission cell 1b in the conventional wireless network;

FIG. 2 illustrates a first embodiment of the present invention;

FIG. 3 illustrates the super frame of the first embodiment;

FIG. 4A illustrates a configuration of the pilot pattern of the firstembodiment;

FIGS. 4B-4I illustrate variations of the configuration of the pilotpattern of the first embodiment;

FIG. 5A illustrates another configuration of the pilot pattern of thefirst embodiment;

FIGS. 5B-5D illustrate variations of the another configuration of thepilot pattern of the first embodiment;

FIGS. 6A-6B illustrate a second embodiment of the present invention;

FIG. 7 illustrates a third embodiment of the present invention;

FIG. 8 illustrates the pilot structures of the first embodiment; and

FIG. 9 illustrates a fourth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following description, the present invention will be explainedwith reference to embodiments thereof. However, these embodiments arenot intended to limit the present invention to any specific environment,applications or particular implementations described in theseembodiments. Therefore, descriptions of these embodiments are onlyintended to illustrate rather than to limit the present invention. Itshould be appreciated that, in the following embodiments and theattached drawings, elements not related directly to the presentinvention are omitted from illustration; and dimensional relationshipsamong individual elements in the attached drawings are illustrated onlyfor ease of understanding, but not to limit the actual scale.

A first embodiment of the present invention is shown in FIG. 2, which isa schematic view of an MIMO network 2. The MIMO network 2 comprises a BS21 and an SS 23. The SS 23 is within a signal coverage of the BS 21. Itshould be noted that, in this embodiment, the MIMO network 2 justcomprises the BS 21 and the SS 23 for description convenience. In otherembodiment, the MIMO network 2 may further comprise other BSs and SSs,the operations and functions thereof are similar to those of the BS 21and the SS 23. Peoples skilled in the art can understand easilyaccording to the description in this embodiment.

First, the downlink (DL) transmission between the BS 21 and the SS 23 isdescribed. The BS 21 comprises a storage module 211, a generation module213 and a transceiver 215. The storage module 211 is configured to storeresource allocation information 210 about the MIMO network 2 and an SSlist 212. The resource allocation information 210 is used to records howthe resource of the MIMO network 2 allocates currently. The SS list 212is used to record the basic information, such as the identifier (ID), ofall SSs (including the SS 23) in the MIMO network 2.

To transmitting DL data to the SS 23, the generation module 213 of theBS 21 is configured to generate a super frame 214 corresponding to theSS 23 according to the resource allocation information 210 and the SSlist 212. The super frame 214 being generated by the generation module213 comprises an interference-reducing (IR) zone. The IR zone comprisesa pilot pattern.

For more details, please refer to FIG. 3, which is a schematic view ofthe super frame 214. In FIG. 3, FH represents “Frame Header”, F0-F3represent “Frames 0-3” respectively, SFM represents “Sub-Frame Map”,DLSF0-DLSF4 represent “DownLink Sub-Frames 0-4” respectively, IRRrepresents “Interference Reducing Request” and ULSF5-ULSF7 represent“UpLink Sub-Frames 5-7” respectively. The super frame 214 furthercomprises switch points 214 a and 214 b. In the following description,only differences from the conventional techniques will be described, andthe portions of the super frame 214 identical with those of theconventional techniques are omitted from description herein andunderstood by peoples skilled in the art easily.

To reducing or avoiding interference of the data transmission, thepresent invention provides the IR zone (i.e. frame F1) in the superframe 214. The IR zone of the super frame 214 comprises a pilot pattern216 which is arranged as an identifier of the SS 23. The pilot patterncomprises a plurality of pilots and data, where each pilot comprisesmitigation information, the functions of which will be described later.The configuration of the pilot pattern may be presented as shown in FIG.4A. In FIG. 4A, the horizontal axis represents “symbol”, the verticalaxis represents “subcarrier”, the gray grid represents a pilot and thewhite grid represents data. In this embodiment, since each of the BS 21and the SS 23 uses two antennas to communicate, the configuration of thepilot pattern will be simplified as shown in FIGS. 4B-4I which justillustrates the pilot parts of FIG. 4A.

For example, FIG. 4B illustrates eight possible pilot patterns, each ofwhich has six pilot structures. Since the each of the BS 21 and the SS23 uses two antennas to communicate, each pilot structure has two pilots(FIG. 4B shows them in nonwhite grid). Each pilot pattern in FIG. 4B canbe considered as an identifier of the SS 23. In other words, the pilotpatterns in FIG. 4B can be identifiers of eight SSs respectively.Similarly, each of the pilot patterns in FIGS. 4B-4I can be anidentifier of an SS.

Please refer to FIG. 5A, which shows another configuration of the pilotpattern. In FIG. 5A, the horizontal axis represents “symbol”, thevertical axis represents “subcarrier”, the gray grid represents a pilotand the white grid represents data. The configuration of the pilotpattern will also be simplified as shown in FIGS. 5B-5D which justillustrates the pilot parts of FIG. 5A. Similarly, each of the pilotpatterns in FIGS. 5B-5D can be an identifier of an SS.

After the generation module 213 of the BS 21 generates the super frame214, the transceiver 215 configured to transmit the DL data to the SS 23by the super frame 214 so that the SS 23 may receive the DL data afterconfirming the pilot pattern of the super frame 214 matches theidentifier of the SS 23. Particularly, the SS 23 comprises a transceiver231 and a confirmation module 233. The transceiver 231 of the SS 23 isconfigured to receive the pilot pattern 216 of the super frame 214. Thenthe confirmation module 233 is configured to confirm whether the pilotpattern 216 of the super frame 214 matches the identifier of the SS 23and then generate a confirmation result 230.

If the confirmation result 230 indicates the pilot pattern 216 of thesuper frame 214 matches the identifier of the SS 23, the transceiver 231is further configured to receive the DL data according to theconfirmation result 230. In addition, since each of pilots in the pilotpattern 216 comprises the mitigation information, the transceiver 231 isfurther configured to overcome a transmission interference of the DLdata according to the mitigation information after receiving the DLdata.

Now the uplink (UL) transmission between the BS 21 and the SS 23 isdescribed. The transceiver 231 of the SS 23 is further configured totransmit a UL data to the BS 21 by the super frame 214. Similar to theDL transmission between the BS 21 and the SS 23, the transceiver 215 ofthe BS 21 is configured to receive the pilot pattern 216 of the superframe 214 and confirm whether the pilot pattern 216 of the super frame214 matches the ID of the SS 23. If so, the transceiver 215 of the BS 21will receive the UL data and further overcome the transmissioninterference of the UL data according to the mitigation informationafter receiving the UL data.

A second embodiment of the present invention is shown in FIGS. 6A-6B,which is a flow chart of a transmission method for use in the MIMOnetwork 2 of the first embodiment. First, step 300 is executed togenerate a super frame corresponding to the SS 23 according to theresource allocation information and the SS list. The super framecomprises a pilot pattern being arranged as an identifier of the SS 23.Step 301 is executed to generate an IR zone in the super frame, wherethe IR zone comprises the pilot pattern. Step 302 is executed totransmit DL data to the SS 23 by the super frame.

Then step 303 is executed to receive the pilot pattern of the superframe. Step 304 is executed to confirm whether the pilot pattern of thesuper frame matches the identifier of the SS 23 and generates aconfirmation result. If the confirmation result is negative, step 305 isexecuted to stop receiving the DL data. If the confirmation result ispositive, step 306 is executed to receive the DL data according to theconfirmation result. Since the pilot pattern comprises a plurality ofpilots, each of which comprises mitigation information, step 307 isexecuted to overcome a transmission interference of the DL dataaccording to the mitigation information after receiving the DL data.

Step 308 is executed to transmitting a UL data to the BS 21 by the superframe. Step 309 is executed to receive the UL data after confirming thepilot pattern of the super frame matches the identifier of the SS 23.Finally, step 310 is executed to overcome a transmission interference ofthe UL data according to the mitigation information after receiving theUL data.

In addition to the steps shown in FIGS. 6A and 6B, this embodiment canalso execute all the operations and functions of the above embodiments.Those of ordinary skill in the art will readily know how to execute thecorresponding operations and functions in this embodiment by consideringthose in the first embodiment; therefore, a detailed description will beomitted here.

The method described above may be embodied in a computer readable mediumstoring the previously described computer program to execute the abovesteps. The computer readable medium may be a soft disk, a hard disk, acompact disk, a mobile disk, a magnetic tape, a database accessible viaa network, or any storage medium that is known to those skilled in theart to have similar functions.

A third embodiment of the present invention is shown in FIG. 7, which isa schematic view of an MIMO network 7. The MIMO network 7 comprises a BS(i.e. the BS 71 in FIG. 7), another BS (i.e. BS 72 in FIG. 7) and a SS73. The BS 71 comprises a storage module 711, a generation module 713and a transceiver 715. The storage module 711 is configured to storepilot structure information 714 recording the information about thepilot structures of the BS 71 and the BS 72. The SS 73 is within asignal coverage between the BS 71 and the BS 72.

For the convenience of following description, it is assumed that the SS73 is communicating with the BS 71 and the BS 72 at the same time for ahandover procedure. In other embodiments, the SS 73 may communicate withBSs 71, 72 at the same time in different procedures. People skilled inthe art may understand it according to the description in thisembodiment.

Based on the above assumption, the SS 73 is handovering from the BS 72to the BS 71. Before starting the handover procedure, the BS 72 iscommunicating with the SS 73 by at least one first pilot structure in afirst super frame 724. After starting the handover procedure, the SS 73has to communicate with the BS 71 and the BS 72 simultaneously. In orderto avoid the transmission interference while the SS 73 is communicatingwith the BS 71 and the BS 72, the transceiver 715 of the BS 71 isconfigured to receive the first super frame 724 to know the at least onefirst pilot structure.

The generation module 713 is configure to select at least one secondpilot structure of a second super frame 714 according to the pilotstructure information 712 and the at least one first pilot structure ofthe first super frame 724 to generate the second super frame 714 withthe at least one second pilot structure, wherein the at least one secondpilot structure is orthogonal to the at least one first pilot structure.After generating the second super frame 714, the transceiver 715 of theBS 71 may communicates with the SS 73 by the second super frame 714avoid a transmission interference between the BS 71 and the BS 72.

More particularly, please refer to FIG. 8 together. As described inaforementioned embodiments, the first super frame 724 may comprise apilot pattern like the one shown in FIG. 4A. The pilot pattern comprisedin the first super frame 724 may be divided into three sub-channels751-753 in frequency. Each of sub-channels 751-753 may comprise a firstpilot structure, i.e. first pilot structure 7241, first pilot structure7242 and first pilot structure 7243. Each first pilot structure maycomprise a plurality of pilots (such as the gray grids and the stripegrids of FIG. 8), each of which comprises mitigation information so thatthe SS 73 may overcome the transmission interference according to themitigation information. Similar to the first super frame 724, the secondsuper frame 714 comprises second pilot structures 7141-7143.

In addition, as shown in FIG. 8, the second pilot structure 7141 isorthogonal to the first pilot structure 7241 to avoid the transmissioninterference. The pilot structure information 712 of the storage module711 is to record the corresponding relation of the first pilotstructures 7241-7243 and the second pilot structures 7141-7143 as shownin FIG. 8. Hence, after the transceiver 715 receives the first superframe 724, the generation module 713 may know the at least one firstpilot structure of the first super frame 724 is like the first pilotstructure 7241, and then select the at least one second pilot structureof the second super frame 714, which is like the second pilot structure7141, according to the pilot structure information 712 and the firstpilot structure 7241.

Herein, the transceiver 715 of the BS 71 may communicates with the SS 73by the second super frame 714 with the at least one second pilotstructure (i.e. second pilot structure 7141) to avoid the transmissioninterference between the BS 71 and the BS 73. In addition, thegeneration module 713 is further configured to generate aninterference-reducing (IR) zone in the second super frame 714, and theIR zone comprises the at least one second pilot structure. The IR zoneis explained in aforementioned embodiments and not described again.

A fourth embodiment of the present invention is shown in FIGS. 9A-9B,which is a flow chart of a transmission method for use in a BS of a MIMOnetwork, such as the BS 71 of the MIMO network 7 in the thirdembodiment. The BS comprises a transceiver, a storage module and ageneration module. The storage module stores pilot structureinformation. The MIMO network system includes another BS and an SS. TheSS is within a signal coverage between the BS and the another BS. Theanother BS communicates with the SS by at least one first pilotstructure in a first super frame.

The transmission method of this embodiment comprises the followingsteps. First, step 901 is executed to enable the transceiver to receivethe first super frame. Step 902 is executed to enable the generationmodule to generate the second super frame. Step 903 is executed toenable the generation module to generate an IR zone in the second superframe. Step 904 is executed to enable the generation module to generatethe at least one second pilot structure in the IR zone of the secondsuper frame.

The steps 902-904 may be considered as a step of enabling the generationmodule to select at least one second pilot structure of a second superframe according to the pilot structure information and the at least onefirst pilot structure of the first super frame to generate the secondsuper frame with the at least one second pilot structure. Finally, step905 is executed to enable the transceiver to communicate with the SS bythe second super frame with the at least one second pilot structure toavoid a transmission interference between the BS and the another BS. Inaddition, the at least one second pilot structure comprises a pluralityof pilots, each of which comprises mitigation information so that the SSmay further overcome the transmission interference according to themitigation information.

In addition to the steps shown in FIG. 9, this embodiment can alsoexecute all the operations and functions of the third embodiment. Thoseof ordinary skill in the art will readily know how to execute thecorresponding operations and functions in this embodiment by consideringthose in the third embodiment; therefore, a detailed description will beomitted here.

The method described above may be embodied in a computer readable mediumstoring the previously described computer program to execute the abovesteps. The computer readable medium may be a soft disk, a hard disk, acompact disk, a mobile disk, a magnetic tape, a database accessible viaa network, or any storage medium that is known to those skilled in theart to have similar functions.

The present invention arranges a pilot pattern, which comprises aplurality of pilots, of the super frame as an identifier of an SS. Nomatter data transition in the TDD, FDD, the central zone edge or thecell zone edge, the BS and the SS will confirm whether the pilot patternof the super frame matches the identifier of the SS which the BS/SSattempts to communicate with. If the confirmation result is positive,the communication will be proceeded. If the confirmation result isnegative, the communication will be terminated. By confirming the pilotpattern, interference of transmission in the MIMO network will bereduced effectively, and the quality of communications will be enhancedeffectively.

Furthermore, the present invention uses different pilot structures,which are orthogonal to each other, in the BSs to transmit the data tothe SS. These two different BSs may communicate with an SS in differentfrequency/channel by using the different pilot structures orthogonal toeach other. The transmission interference, which occurs when the SS iscommunicating with the different BSs at the same time, may be reducedeffectively. Thereby, the defects of the conventional technique may beovercome effectively, and the quality of communications may be enhancedobviously.

The above disclosure is related to the detailed technical contents andinventive features thereof. People skilled in this field may proceedwith a variety of modifications and replacements based on thedisclosures and suggestions of the invention as described withoutdeparting from the characteristics thereof. Nevertheless, although suchmodifications and replacements are not fully disclosed in the abovedescriptions, they have substantially been covered in the followingclaims as appended.

1. A base station (BS) for use in a multi-input multi-output (MIMO)network, the MIMO network including another BS and a subordinatedstation (SS), the SS being within a signal coverage between the BS andthe another BS, the another BS communicating with the SS by at least onefirst pilot structure in a first super frame, the BS comprising: atransceiver, being configured to receive the first super frame; astorage module, being configured to store pilot structure information;and a generation module, being configured to select at least one secondpilot structure of a second super frame according to the pilot structureinformation and the at least one first pilot structure of the firstsuper frame to generate the second super frame with the at least onesecond pilot structure; wherein the at least one second pilot structureis orthogonal to the at least one first pilot structure, the transceiverof the BS may communicates with the SS by the second super frame withthe at least one second pilot structure to avoid a transmissioninterference between the BS and the another BS.
 2. The BS as claimed inclaim 1, wherein the at least one second pilot structure comprises aplurality of pilots, each of the pilots comprises mitigation informationso that the SS may further overcome the transmission interferenceaccording to the mitigation information.
 3. The BS as claimed in claim1, wherein the generation module is further configured to generate aninterference-reducing (IR) zone in the second super frame, the IR zonecomprises the at least one second pilot structure.
 4. A transmissionmethod for use in a BS of an MIMO network, the BS comprising atransceiver, a storage module and a generation module, the storagemodule storing pilot structure information, the MIMO network systemincluding another BS and an SS, the SS being within a signal coveragebetween the BS and the another BS, the another BS communicating with theSS by at least one first pilot structure in a first super frame, thetransmission method comprising the following steps of: (a) enabling thetransceiver to receive the first super frame; (b) enabling thegeneration module to select at least one second pilot structure of asecond super frame according to the pilot structure information and theat least one first pilot structure of the first super frame to generatethe second super frame with the at least one second pilot structure; and(c) enabling the transceiver to communicate with the SS by the secondsuper frame with the at least one second pilot structure to avoid atransmission interference between the BS and the another BS.
 5. Thetransmission method as claimed in claim 4, wherein the ay least onesecond pilot structure comprises a plurality of pilots, each of thepilots comprises mitigation information so that the SS may furtherovercome the transmission interference according to the mitigationinformation.
 6. The transmission method as claimed in claim 4, whereinthe step (b) comprising the following steps of: enabling the generationmodule to generate the second super frame; enabling the generationmodule to generate an IR zone in the second super frame; and enablingthe generation module to generate the at least one second pilotstructure in the IR zone of the second super frame.